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Watchdog Documentation Release 0.9.0 watchdog Documentation Release 0.9.0 Yesudeep Mangalapilly Oct 30, 2019 Contents 1 Directory monitoring made easy with3 2 Easy installation 5 3 User’s Guide 7 3.1 Installation................................................7 3.2 Quickstart................................................ 10 3.3 API Reference.............................................. 10 3.4 Contributing............................................... 21 4 Contribute 23 5 Indices and tables 25 Python Module Index 27 Index 29 i ii watchdog Documentation, Release 0.9.0 Python API library and shell utilities to monitor file system events. Works on Python 2.7 and 3.4+. If you want to use an old version of Python, you should stick with watchdog < 0.10.0. Contents 1 watchdog Documentation, Release 0.9.0 2 Contents CHAPTER 1 Directory monitoring made easy with • A cross-platform API. • A shell tool to run commands in response to directory changes. Get started quickly with a simple example in Quickstart. 3 watchdog Documentation, Release 0.9.0 4 Chapter 1. Directory monitoring made easy with CHAPTER 2 Easy installation You can use pip to install watchdog quickly and easily: $ pip install watchdog Need more help with installing? See Installation. 5 watchdog Documentation, Release 0.9.0 6 Chapter 2. Easy installation CHAPTER 3 User’s Guide 3.1 Installation watchdog requires Python 2.7 or 3.4+ to work. If you are using a Linux/FreeBSD/Mac OS X system, you already have Python installed. However, you may wish to upgrade your system to Python 2.7 at least, because this version comes with updates that can reduce compatibility problems. See a list of Dependencies. 3.1.1 Installing from PyPI using pip $ python -m pip install watchdog # or to install the watchmedo utility: $ python -m pip install |project_name|[watchmedo] 3.1.2 Installing from source tarballs $ wget -c http://pypi.python.org/packages/source/w/watchdog/watchdog-0.9.0. ,!tar.gz $ tar zxvf watchdog-0.9.0.tar.gz $ cd watchdog-0.9.0 $ python -m pip install -e . # or to install the watchmedo utility: $ python -m pip install -e .[watchmedo] 3.1.3 Installing from the code repository 7 watchdog Documentation, Release 0.9.0 $ git clone --recursive git://github.com/gorakhargosh/watchdog.git $ cd watchdog $ python -m pip install -e. # or to install the watchmedo utility: $ python -m pip install -e.[watchmedo] 3.1.4 Dependencies watchdog depends on many libraries to do its job. The following is a list of dependencies you need based on the operating system you are using. Operating system Windows Linux 2.6 BSD Mac OS X/ Dependency (row) Darwin XCode Yes pathtools Yes Yes Yes Yes The following is a list of dependencies you need based on the operating system you are using the watchmedo utility. Operating system Windows Linux 2.6 BSD Mac OS X/ Dependency (row) Darwin PyYAML Yes Yes Yes Yes argh Yes Yes Yes Yes Installing Dependencies The watchmedo script depends on PyYAML which links with LibYAML. On Mac OS X, you can use homebrew to install LibYAML: brew install libyaml On Linux, use your favorite package manager to install LibYAML. Here’s how you do it on Ubuntu: sudo aptitude install libyaml-dev On Windows, please install PyYAML using the binaries they provide. 3.1.5 Supported Platforms (and Caveats) watchdog uses native APIs as much as possible falling back to polling the disk periodically to compare directory snapshots only when it cannot use an API natively-provided by the underlying operating system. The following operating systems are currently supported: Warning: Differences between behaviors of these native API are noted below. 8 Chapter 3. User’s Guide watchdog Documentation, Release 0.9.0 Linux 2.6+ Linux kernel version 2.6 and later come with an API called inotify that programs can use to monitor file system events. Note: On most systems the maximum number of watches that can be created per user is limited to 8192. watchdog needs one per directory to monitor. To change this limit, edit /etc/sysctl.conf and add: fs.inotify.max_user_watches=16384 Mac OS X The Darwin kernel/OS X API maintains two ways to monitor directories for file system events: • kqueue • FSEvents watchdog can use whichever one is available, preferring FSEvents over kqueue(2). kqueue(2) uses open file descriptors for monitoring and the current implementation uses Mac OS X File System Monitoring Performance Guidelines to open these file descriptors only to monitor events, thus allowing OS X to unmount volumes that are being watched without locking them. Note: More information about how watchdog uses kqueue(2) is noted in BSD Unix variants. Much of this information applies to Mac OS X as well. BSD Unix variants BSD variants come with kqueue which programs can use to monitor changes to open file descrip- tors. Because of the way kqueue(2) works, watchdog needs to open these files and directories in read-only non-blocking mode and keep books about them. watchdog will automatically open file descriptors for all new files/directories created and close those for which are deleted. Note: The maximum number of open file descriptor per process limit on your operating system can hinder watchdog’s ability to monitor files. You should ensure this limit is set to at least 1024 (or a value suitable to your usage). The following command appended to your ~/.profile configuration file does this for you: ulimit-n 1024 Windows Vista and later The Windows API provides the ReadDirectoryChangesW. watchdog currently contains implementation for a synchronous approach requiring additional API functionality only available in Windows Vista and later. Note: Since renaming is not the same operation as movement on Windows, watchdog tries hard to convert re- names to movement events. Also, because the ReadDirectoryChangesW API function returns rename/movement events for directories even before the underlying I/O is complete, watchdog may not be able to completely scan the moved directory in order to successfully queue movement events for files and directories within it. Note: Since the Windows API does not provide information about whether an object is a file or a directory, delete events for directories may be reported as a file deleted event. OS Independent Polling watchdog also includes a fallback-implementation that polls watched directories for changes by periodically comparing snapshots of the directory tree. 3.1. Installation 9 watchdog Documentation, Release 0.9.0 3.2 Quickstart Below we present a simple example that monitors the current directory recursively (which means, it will traverse any sub-directories) to detect changes. Here is what we will do with the API: 1. Create an instance of the watchdog.observers.Observer thread class. 2. Implement a subclass of watchdog.events.FileSystemEventHandler (or as in our case, we will use the built-in watchdog.events.LoggingEventHandler, which already does). 3. Schedule monitoring a few paths with the observer instance attaching the event handler. 4. Start the observer thread and wait for it generate events without blocking our main thread. By default, an watchdog.observers.Observer instance will not monitor sub-directories. By passing recursive=True in the call to watchdog.observers.Observer.schedule() monitoring entire direc- tory trees is ensured. 3.2.1 A Simple Example The following example program will monitor the current directory recursively for file system changes and simply log them to the console: import sys import logging from watchdog.observers import Observer from watchdog.events import LoggingEventHandler if __name__ =="__main__": logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(message)s', datefmt='%Y-%m-%d %H:%M:%S') path= sys.argv[1] if len(sys.argv)>1 else '.' event_handler= LoggingEventHandler() observer= Observer() observer.schedule(event_handler, path, recursive=True) observer.start() try: while observer.isAlive(): observer.join(1) except KeyboardInterrupt: observer.stop() observer.join() To stop the program, press Control-C. 3.3 API Reference 3.3.1 watchdog.events module watchdog.events synopsis File system events and event handlers. author [email protected] (Yesudeep Mangalapilly) 10 Chapter 3. User’s Guide watchdog Documentation, Release 0.9.0 Event Classes class watchdog.events.FileSystemEvent(src_path) Bases: object Immutable type that represents a file system event that is triggered when a change occurs on the monitored file system. All FileSystemEvent objects are required to be immutable and hence can be used as keys in dictionaries or be added to sets. event_type = None The type of the event as a string. is_directory = False True if event was emitted for a directory; False otherwise. is_synthetic = False True if event was synthesized; False otherwise. These are events that weren’t actually broadcast by the OS, but are presumed to have happened based on other, actual events. src_path Source path of the file system object that triggered this event. class watchdog.events.FileSystemMovedEvent(src_path, dest_path) Bases: watchdog.events.FileSystemEvent File system event representing any kind of file system movement. dest_path The destination path of the move event. class watchdog.events.FileMovedEvent(src_path, dest_path) Bases: watchdog.events.FileSystemMovedEvent File system event representing file movement on the file system. class watchdog.events.DirMovedEvent(src_path, dest_path) Bases: watchdog.events.FileSystemMovedEvent File system event representing directory movement on the file system. class watchdog.events.FileModifiedEvent(src_path) Bases: watchdog.events.FileSystemEvent File system event representing
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